The brown-leaved rosemary plants might have suffered some branch dieback due to a cold snap earlier this winter, so it's hard to tell quite yet if they are still alive. Once we reach the single digits in overnight temperature, rosemary tends to succumb to the cold, though some varieties are a bit more cold-tolerant than others. Overall, we're on the edge of their winter hardiness here in MD and DC. For now, avoid trimming until you see signs of new growth in spring, otherwise it may be hard to tell if branches with brown leaves are truly dead or just have to replace foliage. Given the extent of the damage, we suspect the plants will either have to leaf-out anew from their base, such as growing new stems directly from the root system, or will be so weakened by significant amounts of dieback they will need replacement. As for how much to prune, that will depend on what stems remain leafless and presumed dead after any spring new growth appears. The timing of new growth can be weather-dependent, but any live buds along the stems will probably begin growth sometime in April (May at the latest).

The same is true for lavender: while a bit more cold-hardy, they too can occasionally suffer branch dieback over the winter. Both rosemary and lavender are very sensitive to the soil staying too wet or draining poorly, so sometimes this is a factor in winter dieback when cold by itself was not. As "sub-shrubs" (somewhere between perennials which can be cut completely back in winter and shrubs which are not cut back) their pruning is tricky, and only completely dead growth should be removed when pruning. Sometimes you can shorten branches, but the cuts should be make within the part of the branch end that is still leafy, as pruning cuts into older, lower, leafless wood tend not to result in regrowth. Therefore, they often can't be cut back very far in order to refresh the plant's appearance with new branch growth. It's normal for both rosemary and lavender to get a bit leggy-stemmed with age, meaning their oldest, lower leaves will die off (naturally, regardless of winter conditions) and remain bare for the life of that branch. The lower leaf browning on the lavender might be due to this process, in which case they'll eventually fall off on their own.

Leaf loss on evergreens like these is also sometimes exacerbated by prior damage from pests like spider mites, leafhoppers, and thrips, any of which can be common on herbs like rosemary and lavender. The damage can be hard to detect until it's extensive, and may be one reason leaves brown or shed prematurely during the growing season or become vulnerable to damage in winter.

For now, we recommend just letting the dead leaves fall off on their own, though you might be able to speed-up the process for aesthetics and knock them off by using your hand to brush them off the stem. If they don't detach, they are not ready to fall yet (if the stem is alive) or the entire stem has died, though it may be too early to tell which is the case here.

The container for the lavender appears to be sitting on top of a saucer which has collected water. We suggest that either outdoor containers not use saucers since they're often not needed (compared to indoor plants where you want to contain drips), or that saucers get emptied promptly after watering or precipitation so the collected water doesn't seep back into the soil and risk drowning roots. Once root rot has begun triggered by soggy soil, it cannot be directly treated, so it's best to reduce the risk by avoiding situations that keep the soil too wet.

Miri

Hi Miri,

You're welcome!